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Owners of Mercedes E200 2003/4 Petrol - request for simple test

  • 15-08-2011 6:09pm
    Registered Users Posts: 33 POE101


    Do you own (or do you know someone close by who owns) a Mercedes E200 2003/4 (1.8 petrol engined kompressor - automatic)
    If so I would greatly appreciate 5 minutes of your time to perform a simple test and let me know the results.
    I will explain why if/when I have some results in...

    The E200 model changed in 2003 and I am only interested in the newer one (W211) as the older model may not be relevant to the test.

    The test itself is a simple one but **PLEASE DO NOT put the key in the ignition until you reach the 3rd step in the test**

    I would like to know how much brake pedal travel there is before the engine is started and if the pedal pulls down when the engine is started.
    Also, as an aside, at what stage does the SBC unit kick in (the purring or light grinding noise that comes from the aluminium box in the engine
    bay over the driverside wheel).

    What to do ..

    1 Standing outside the car, unlock it using the remote keypad.

    2 Sit in the car, depress the brake and note approximately how much brake pedal travel there is.

    3 **Keeping your foot on the brake pedal** put the key in the ignition and turn on the engine. Did the brake pedal suck down when the engine started?

    4 Reply to this post with results

    Thats all I would like to know and I would appreciate it if you would confirm year and model of car - again I will explain why I am interested after I have some results in.

    Many thanks in advance.



  • Closed Accounts Posts: 12,811 ✭✭✭✭ Slidey

    The pedal will normally drop when you start any car after it has been stopped long enough for the vacuum to leak.

    If you feel the abs is cutting in too soon, you probably have an ABS sensor with too large a gap between it and the rotor of else a dirty sensor

  • Registered Users Posts: 33 POE101

    Thanks for the quick response Slidey.

    I'm intrigued (a little bit of knowledge ... and that's all I have I'm not a mechanic but like to know how things work)

    Can the ABS affect brake operation even when the car is static?
    I'm assuming the sensors are on the brake calipers somewhere and if so if I remove each wheel, locate and wipe the sensors (if possible), you think it might change the pedal behaviour?

  • Registered Users Posts: 554 ✭✭✭ crosshair1

    "Did the brake pedal suck down when the engine started?"

    It shouldnt, there shouldnt be a servo fitted to this, they are fitted with SBC and ths amplifys the pressure thats generated in the master cylinder.

    As a side note it must be deactivated before working on the brake system, from memory sometimes the pump will actuate when the drivers door is opened.

  • Closed Accounts Posts: 12,811 ✭✭✭✭ Slidey

    I didn't know that.

    I have heard that about the merc cars before alright, only changed pads in one once and made sure doors remained closed with ignition off

  • Registered Users Posts: 33 POE101

    In the Mercedes E200s (only) between 2002 and 2006 approx, the brake system does not behave conventionally. Usually (as you will no doubt be aware) if you put your foot on the brake pedal and then turn on the engine the pedal will pull down slightly as the servo vacuum builds. These E200s are different -its more like 'drive by wire' and beyond me to explain in any detail but the important point is that ** these cars do not have a brake servo in the conventional sense and the brake pedal does NOT pull down when you start the engine**

    This may be of use to anyone who's E200 has failed NCT despite PASSING on ALL the metrics it was measured on - as mine did (and mine is not the only one).

    In my case the car was failed because in the mechanic's opinion the brake pedal travel was 'wrong' and "unlike all other E200's he has tested" and was probably because the servo was sticking". What has now been confirmed by Mercedes (mechanic who road tested the car & separately by another senior tech in Mercedes) is that the NCT mechanic is very wrong in his diagnosis and clearly is not familiar with how the braking on these E200 works.

    To make matters more interesting the NCT contract changed hands over a year ago and the previous incumbents made the same mistake when they first came across these E200s. So apparently the learnings were not carried through to the new organisation.

    I hope this helps someone else.

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  • Registered Users Posts: 33 POE101

    Crosshair1 Slidey

    Thanks for replies - While researching this problem I came across a Mercedes document that details a complex sequence of actions/codes to be followed in order to disable the SBC before working on the brakes including things like locking and unlocking the drivers door, opening the drivers window putting key in the ignition turning lights from auto to off and a few other stages that requires TWO people to complete with a very clear warning that the car doors must not be unlocked while any work is being carried out on the brakes. As far as I know the SBC has it's own backup battery as well so disconnecting the car battery won't even disable it. Handle with extreme care lest you get sprayed with brake fluid or lose a finger.

  • Registered Users Posts: 554 ✭✭✭ crosshair1

    These are 8 year old systems now, the procedure you describe afaik is directed towards developing countries that dont have merc service. The proper method is using a scantool and this has been available for years on generic tools. Also sbc units are still fully covered on goodwill through the agents.